The present disclosure relates to surgical devices, and more particularly, to a bone anchoring device.
U.S. Pat. No. 5,005,562 discloses a bone anchoring device having a threaded shaft or a hook to be anchored in the bone and a head formed integrally with the shaft, the head having a U-shaped recess for receiving a rod. This so-called monoaxial bone anchoring device has a high resistance to loads. However, the possibility to adjust the position of the head to the anatomical conditions is limited.
U.S. Pat. No. 5,443,467 discloses a bone anchoring device comprising a receiving part for receiving a rod and a bone anchoring element having a threaded shaft and a spherical head which is pivotably held in the receiving part. With this so-called polyaxial bone anchoring element the anchoring member can be pivoted in a range of generally up to about ±25° about the longitudinal axis of the receiving part in directions in a range of 360° around the longitudinal axis. Therefore, it is possible that even after screwing-in the threaded section of the bone anchoring member into the bone the adjustment of the orientation of the receiving part relative to the anchoring element in order to receive the rod is possible. After the orientation of the receiving part has been adjusted to the anatomical conditions and the rod has been inserted into the receiving part, the bone anchoring device is locked.
US 2006/0155277 A1 describes an anchoring element, which comprises a retaining means for receiving a rod, the retaining means having a ring-shaped mount, a fastening element for anchoring the device in the vertebra, and a securing element which can be screwed into a thread of the retaining means in order to fix the fastening element with an angle relative to the retaining means. The fastening element comprises a threaded shank and a bearing, the latter being provided to achieve a pivotal motion when being supported by a separate intermediate element, which can be inserted into the ring-shaped mount of the retaining means. More specifically, the bearing includes spherical surfaces which engage with spherical counterparts of the intermediate element. The bearing further has two flat guiding surfaces formed on opposite sides thereof, which engage with respectively flat counter surfaces of the intermediate element. The fastening element may perform a rotation movement around one single axis with respect to the intermediate element. However, the intermediate element can freely rotate within the mount around a longitudinal axis of the retaining means. Hence, a polyaxial adjustment of the fastening element relative to the retaining means is possible. The final fixation is achieved by screwing the securing element into the thread of the retaining means after the rod is inserted. As a result thereof, pressure is exerted onto the rod, which transmits this pressure further to the intermediate element which then frictionally clamps the bearing. Thus, upon fixation by the securing element, the degree of free movement is reduced from polyaxial to fully rigid at the same time.
For certain clinical applications, for example in the region of the cervical vertebrae, due to the small dimensions of the cervical vertebrae, a greater degree of pivoting to one specific side is necessary than it is the case in the region of the larger thoracic vertebrae and lumbar vertebrae. U.S. Pat. No. 6,736,820 B2 discloses a bone screw having a screw member with a threaded section and a head which is pivotably held in a receiving part receiving a rod. The screw member can be pivoted to at least one side by an enlarged angle. This is accomplished by providing an edge of the receiving part with an asymmetric construction. However, the screw member is still pivotable in all directions in a 360° angular range around its screw axis.
An example of a Cosmic Posterior Dynamic System is shown in FIG. 17 that includes a bone anchoring device having a receiving part 100 receiving a rod 101 and a bone screw 102, wherein the bone screw is pivotably held in the receiving part around a pivot axis 103 formed by a transverse pin 105 which is perpendicular to the longitudinal axis 104 of the receiving part and perpendicular to the rod. Hence, the bone screw can be pivoted in a single plane containing the longitudinal axis of the receiving part. The position of the bone screw relative to the receiving part cannot be locked and therefore, the bone screw and the receiving part are movable relative to each other all the time.
In view of the above, there is a need for a bone anchoring device which can be adjustable, which can have an improved load resistance, can be easy to handle and safe to lock the angled position of the bone screw.